State media official line says Mugabe has started his annual leave which will run up to the end of January next year.

Robert Mugabe has been to Singapore seeking treatment for what has been described as a serious ailment which requires constant monitoring by specialists in Asia.

He has travelled to Singapore quite a few times this year for what his officials described as routine check-ups following an operation to correct a cataract problem.

In a statement, his spokesperson, George Charamba said the President will spend part of his leave in the Far East together with his family.

A source in the President's office confirmed to the Zimbabwe Mail that Mugabe, who normally takes his leave in January, will take part in a series of medical treatments for as many weeks.

Meanwhile, Vice President Joice Mujuru is the Acting President.

Confidential cables leaked by the whistle-blowing website Wikileaks suggest that Zimbabwean leader Robert Mugabe is gravely ill with prostate cancer.

Extracts from the leaked cables were published by numerous Zimbabwe news outlets.

"According to Gono, Mugabe's doctor had recommended he cut back on his activities. (NOTE: Gono told us last year that Mugabe was ill and that his doctor had urged him to step down immediately. Mugabe had told his doctor, according to Gono, that he would leave office after the election)," continued the leaked document.

Wikileaks claimed that Reserve Bank of Zimbabwe Governor Gideon Gono told then-US Ambassador James Mcgee that Mugabe had prostate cancer that had spread to other parts of his body. The cable says the growth "will cause his death in three to five years".

Grace Mugabe, the leader's wife, also told Gono that her spouse was "out of it about 75% of the time", according to one cable. "The governor confided that Mugabe appeared to be deteriorating mentally and losing his capacity to balance factional interests," wrote the ambassador. "She wanted him to step down."

Eddie Cross of the opposition party Movement for Democratic Change (MDC) described Mugabe's illness as an "open secret".

In another cable, Botswana President Ian Khama was quoted as telling US officials that Mugabe fell asleep in meetings, but was always quick to respond when asked questions.

An analyst for a South African democracy institute warned that there would be "no successor with the necessary clout" to win a majority, should Mugabe become gravely ill. He noted: "Mugabe might be incapacitated soon. And without him, there is no chance in hell that ZANU-PF [Mugabe's party] has national standing."

A spokesman for Zanu-PF has in the past responded to the allegations. "If he was that ill, how come he is still going strong?" questioned Rugare Gumbo. "I have seen him for a long time and even last week, he has no health problems. There is a lot of things that are not true in that."

London-based Zanu PF loyalist George Shire expressed doubt that the information would drastically change the Zimbabwean political situation, decrying the cables as "mere gossip".

Reports of Mugabe's failing health are not new; another leaked cable from 2000 discusses rumors of Mugabe collapsing three times while on tour of Africa and en route to New York's Millenium Summit. Some rumors went as far as to say Mugabe had attempted suicide. George Charamba, the president's spokesman, dismissed those reports as an "April Fool's" joke, and said Mugabe was "fit as a fiddle".

Wikileaks says the president received treatment for a urinary tract disorder in 1994 and had an operation in 1996 for throat problems.

By Special correspondent